GREENBUG (HOMOPTERA, APHIDIDAE) RESISTANCE TO PARATHION AND CHLORPYRIFOS-METHYL

Resistance to parathion and chlorpyrifos-methyl of two strains of greenbug, Schizaphis graminum (Rondani), was evaluated using a vial-residue bioassay technique. The tests, repeated three times over a 3-month period, detected resistance to parathion and chlorpyrifos-methyl in a greenbug colony collected from a parathion-failure sorghum field when compared to a 3-year-old, susceptible, greenhouse colony. A gel electrophoresis test indicated that greenbugs from the parathion-failure field had an esterase band 6 times as dense as the band obtained from greenbugs form the susceptible colony. Increased esterase levels are often associated with pesticide resistance in arthropod populations.